Presentation Authors: Dermot O'Kane*, Justin Du Plessis, Graham Baldwin, Arthur Shulkes, Damien Bolton, Oneel Patel, Joseph Ischia, Melbourne, Australia
Introduction: Renal ischaemia reperfusion injury (IRI), is a major source of morbidity and mortality in hospitalised patients. Despite extensive research, there are no effective therapies against renal IRI, and patient outcomes have not improved. Our group have previously demonstrated that zinc (Zn) preconditioning (PC) protects the kidney against renal IRI in a sheep model. However, the mechanisms through which Zn exerts its effect are unknown. There are multiple processes involved in the pathogenesis of renal IRI, and multiple cellular processes affected by Zn. The key putative mechanisms of renal IRI include inflammatory, apoptotic, and oxidative stress pathways. Interleukin-6 (IL-6), Bax & Bak, and glutathione peroxidase-1 (GpX1) are proteins centrally involved in these respective pathways. Our aim was to assess the contribution of these three key mechanisms to Zn&[prime]s protective effect using transgenic mouse strains with knockout (KO) of these key mediators. Furthermore, dysfunctional cellular metal homeostasis has been suggested as a pivotal mechanism of cellular death due to IRI. We thus investigated the effect of Zn PC on renal metal concentrations in the context of IRI.
Methods: 8-12 week old C57BL/6 mice were preconditioned with intraperitoneal injection of ZnCl2 (10mg/kg) or control 24 hrs & 4 hrs prior to right nephrectomy and 30 mins of left renal ischaemia. Animals were euthanised on the second post-operative day. Blood samples were taken for creatinine and urea. Kidneys were taken for histology and tissue metal analysis. The same protocol was applied to three separate C57BL/6 mouse strains, with genetic KO of IL-6, Bax/Bak, or GpX1.
Results: The Zn PC protocol was well tolerated in all strains. Zn-treated mice in all strains had significantly improved renal parameters than saline-treated controls following renal ischaemia suggesting that the protective effect of Zn is not mediated by these three pathways. Significant differences were observed in renal concentrations of Na, Mg, Ca, & Fe as a result of renal IR. Zn PC had no effect on the concentrations of these metals. Renal Zn was 1.46-fold greater in Zn-treated animals (p= < 0.01). Total renal Zn concentration was not significantly affected by IR.
Conclusions: Zn PC is preserved despite KO of IL-6, Bax & Bak, or GpX1. Zn thus does not have its effect solely via these mediators, and may act through a number of mechanisms. Renoprotection with Zn PC is associated with increased Zn uptake in the kidney, but is not attributable to effects on other renal metal concentrations.
Source of Funding: This work was in part supported by the Austin Health Medical Research Foundation and by University of Melbourne.